In the manufacture of semiconductor devices, a substrate composed of an Si (Silicone) wafer, a planar glass, or the like is processed so as to have features of the order of microns or less. Consequently, the attachment of foreign matter (e.g. dust particulate) to the substrate during manufacture may result in an immediate decrease in yield. Thus, a conventional production line for semiconductor devices is wholly installed in a clean room manageably maintained in a clean environment (cleanliness).
However, to keep the whole production line very clean, a large-capacity clean room is required which comprises a large number of cleaning units. High costs are thus required to build a clean room. Further, a cleaning unit composed of a blowing fan, an HEPA (high efficiency particulate air) filter, and others requires high power to drive the blowing fan, thus requiring high running costs. Furthermore, to maintain a uniform cleanliness throughout a large clean room, it is necessary to use a technique for controlling the flow of air using pressure control or the like. It has been difficult to maintain and manage such flow control.
To solve these problems, a local cleaning technique has been used to improve the cleanliness of a part of the production line instead of the whole production line. The local cleaning technique locally increases the cleanliness of only a space in which manufactured articles are moved. With this technique, for example, a space on a passage on which semiconductor devices being manufactured are carried is made cleaner than the other spaces. In this case, costs can be reduced compared to the improvement of cleanliness of the whole line.
Further, the Unexamined Japanese Patent Application Publication (Tokkai-Hei) No. 11-238777 discloses an invention relating to a cassette carrying system achieved by further improving the above local cleaning technique. This system makes the interior of a loader/unloader of a semiconductor manufacturing apparatus and of an automated carrying vehicle cleaner than a clean room in order to reduce costs required to maintain and manage the clean room.
FIG. 17 is a figure schematically showing the configuration of the conventional automated carrying system described in the above publication. A cassette housing section 13 of an automated carrying vehicle 1 and a loader/unloader 21 of a semiconductor manufacturing apparatus 2 are provided with transfer ports 11, 22, respectively, through which a cassette 17 in which Si wafers, glass substrates, and others are stored. The transfer ports 11, 22 are openings with shutters which are formed at the same height so as to have the same shape.
The use of the transfer ports 11, 22 serves to keep the interior of the automated carrying vehicle 1 and semiconductor manufacturing apparatus 2 very clean. Thus, a carrying path and the like have only to be maintained at a relatively low cleanliness. This enables a reduction in costs required to construct, maintain, and manage a clean room.
However, with the method of making the space on the passage on which semiconductor device being manufactured are carried cleaner than the other spaces, when the automated carrying vehicle 1 runs, it may stir up foreign matter on a floor surface. The foreign matter may then be attached to the automated carrying vehicle 1 itself and semiconductor devices in cassettes set at the transfer port of the semiconductor manufacturing apparatus 2. This makes it necessary to blow a stronger down flow against the passage, change the shape of partitioning walls around the periphery of passage, or possibly reduce the speed of the carrying vehicle.
With the conventional automated carrying system described in the above publication, if the cassette 17 is transferred between the automated carrying vehicle 1 and the semiconductor manufacturing apparatus 2, the automated carrying vehicle 1 is moved to a position where the transfer ports 11, 22 of the automated carrying vehicle 1 and semiconductor manufacturing apparatus 2, respectively, stand opposite each other, before the shutters of the automated carrying vehicle 1 and semiconductor manufacturing apparatus 2 are opened. At this time, foreign matter attached to the outside of the shutters may be stirred up. As a result, the stirred-up foreign matter may contaminate that area close to the automated carrying vehicle 1 and semiconductor manufacturing apparatus 2 in which the cassette 17 is to be transferred, notably the vicinity of the transfer ports 11, 22.
Further, when the automated carrying vehicle 1 runs, it may stir up foreign matter on the floor surface. The foreign matter may then be attached to the shutters of the automated carrying vehicle 1 itself and semiconductor manufacturing apparatus 2. Thus, if an attempt is made to increase the running speed of the automated carrying vehicle 1 in order to improve productivity, the contamination of vicinity of the transfer ports may produce more marked adverse effects. This may lead to a decrease in yield.
The present invention is provided in view of the above circumstances. It is an object of the present invention to provide a carrying vehicle and a manufacturing apparatus the interior of which is kept cleaner than a surrounding environment, and a carrying system comprising the carrying vehicle and the manufacturing apparatus, wherein manufactured articles to be transferred are prevented from being contaminated by foreign matter or the like attached to transfer ports.
It is another object of the present invention to provide a carrying vehicle, a manufacturing apparatus, and a carrying system wherein a transfer operation can be started once the carrying vehicle arrives at a transfer point, thus reducing the time required for carriage or the costs of the carrying system or improving productivity.